The invention relates to a discharge booster for slow-flowing bulk material, which is to be unloaded from a container whereby the container comprises a bottom, a discharge port that may be sealed by a shutoff valve, a top, a center piece, and a shaking device.
A known discharge booster depicted in FIG. 2 is disclosed in U.S. Pat. No. 5,875,935 (corresponding to DE 196 41827 C1), the disclosure of which is incorporated herein by reference. That booster, disposed at a lower discharge end of a vessel 10, includes an annular flange 12a coupled to a connecting flange 15a, and a flexible adapter 20a disposed between the flanges 12a, 15a. A shaking device 30 is mounted atop the connecting flange 15a.
The connecting flange 15a constitutes a first connecting piece which is to be releasably connected to a second connecting piece 16a carried by another container. Seals 22a, 24a are mounted at inner surfaces of the connecting pieces 15a, 16a, respectively. The first and second connecting pieces 15a, 16a are respectively provided with a passive shutoff valve 14 and an active shutoff valve 28a, each valve being in the shape of a pivotable sealing flap gate. The gates are moved from a closed position to an open position by an oscillation drive (not shown) connected to the active gate. The active gate thus rotates the passive gate. Movements produced by operation of the drive and the gates produce vibrations that are conducted to the shaking device 30 to vibrate the latter. Vibrators 29a could be mounted on the connecting piece 16 to augment the vibrations.
Vibrations in the container 10 are caused by the movement of the shaking device 30, which will break down, or prevent possible arching of, the bulk material in the container to continuously maintain a bulk material flow for the purpose of emptying the container. It has been found, however, that the known discharge boosters with driven shaking devices still do not guarantee uninterrupted discharging of bulk material from a container. Continuous out-flowing of bulk material is actually prevented when a vacuum is created in a void disposed within the container above the bulk material in response to a discharging of the bulk material.
It is customary at the present to counteract the build-up of a vacuum in that void by providing external ventilation connections, or lifting temporarily the cover of the upper container which seals the upper filler opening. This is, of course, in contradiction with clean air laws, especially when the bulk material is a sensitive material or is hazardous to one's health.
It is therefore the object of the invention to further develop the state of the discharge booster whereby the disadvantages of the current state-of-the-art are overcome and to ventilate the void in a simple manner, without contamination of the environment or the bulk material.